the other thread was an oopsy...i want to dye the tips of my hair, what kinds of things can I use?

I am thirteen and I have been dying my hair with semi-permenent colors for almost a year, and I would like to try something different. I really want to dye the tips of my hair either blue or green. I wanted to know if I could use some sort of food coloring so I can change it often. I went to a website and it said that I could also use Kool-Aid or Jello to acheive this look. How do I use them and how long will they stay in? I go swimming a lot and was also wondering if the color would come out in the pool? If you could help me it would be appreciated!
Thanks!
Eryn

to use these, i think you would add just a bit of water to the powder to make it into a paste and then put it in your hair and wait awhile depending on how intense you want the color.